This invention relates to electrical switches and more particularly to electrical solenoid switches in which a switch operator is caused to move by electromagnetic coils in order to make or break a circuit. In particular, the present invention relates to a solenoid switch which is positively actuated in two directions by a solenoid arrangement.
In certain switch applications, equipment containing a switch might not be used for extended periods of time. It may be further important that the switch be tamper proof to the extent that unauthorized personnel cannot turn the equipment on and, when the equipment has been turned on, the equipment cannot be turned off except under certain circumstances. Thus, while the switch may be periodically tested, the frequency of such testing is necessarily limited in order to reduce costs and to discourage tampering. Long quiescent periods create unique problems of wear and corrosion. The switch must be able to operate in a reasonably "fail-safe" manner when operation of the switched equipment is needed, so it is therefore necessary that such wear and corrosion problems be overcome.
In enhancing the reliability of such switch units, it is important that the switch be able to be operated reliably for a large number of cycles without preventative maintenance. The switch must have arc suppression capabilities. The use of an arc suppression circuit must be avoided because of the possibility that circuit elements within the arc suppression circuit can fail either on their own or with the aid of tampering. Arcing and other contact wear factors become more significant when high current levels, such as 50 amperes, are switched. The effects of pitting and other types of wear on the contact surfaces must also be minimized. Furthermore, these arc suppression problems, which become magnified in outer space environments in which a vacuum is present, must be minimized.